循环队列的实现方法1

设：
队列长度是QUEUE_LENGTH
队列数组是queue[QUEUE_LENGTH]
队列头索引是head
队列尾索引是tail
队列已有元素个数是number

入队：
queue[tail] = 元素;
tail = (tail + 1) % QUEUE_LENGTH;
number += 1;

出队：
元素 = queue[head];
head = (head + 1) % QUEUE_LENGTH;
number -= 1;

判断队列空：
if(number == 0){...}

判断队列满：
if(number >= QUEUE_LENGTH){...}

举例：

#include <stdio.h>
#include <string.h>

#define QUEUE_LENGTH 16

typedef struct {
  unsigned char *data;
  unsigned int   size;
} SOUND_T;

typedef struct {
  SOUND_T  array[QUEUE_LENGTH];
  unsigned head;
  unsigned tail;
  unsigned number;
} QUEUE_T;

//循环队列初始化
void queue_init(QUEUE_T *queue){
  memset(queue, 0, sizeof(QUEUE_T));
}

//判断队列是否空
unsigned queue_isEmpty(QUEUE_T *queue){
  return queue->number == 0 ? 1 : 0;
}

//判断队列是否满
unsigned queue_isFull(QUEUE_T *queue){
  return queue->number >= QUEUE_LENGTH ? 1 : 0;
}

//获取队列已有成员数
unsigned queue_getNumber(QUEUE_T *queue){
  return queue->number;
}

//入队
void queue_put(QUEUE_T *queue, SOUND_T *sound){
  queue->array[queue->tail] = *sound;
  queue->tail = (queue->tail + 1) % QUEUE_LENGTH;
  queue->number += 1;
}

//出队
void queue_get(QUEUE_T *queue, SOUND_T *sound){
  *sound = queue->array[queue->head];
  queue->head = (queue->head + 1) % QUEUE_LENGTH;
  queue->number -= 1;
}

记于 2019-02-14